US patent application US 2014/0159273 A1 discloses a filament drive mechanism for use with an additive manufacturing system. The filament drive mechanism comprises first and second drive shafts engaged with each other and configured to rotate in opposing rotational directions around substantially parallel axes that are spaced apart at a fixed offset distance. The first and second drive shafts comprise engagement surfaces substantially aligned with each other for engaging a consumable filament arranged there between. The engagement surfaces are textured surfaces for engagement with the consumable filament, wherein the filament is at least partially compressed at a filament surface at one or more locations concurrently. In a preferred embodiment the engagement surfaces comprise linearly knurled surfaces with a plurality of teeth extending radially around the first and second drive shafts.
US patent application US 2007/0003656 A1 discloses a deposition modelling system that utilizes a drive mechanism to feed a strand of filament to create a model. The drive mechanism comprises a pivot block that is rotatable connected to a fixed block and a motor that rotates a drive shaft. A drive roller is connected to the drive shaft and an idler roller is connected to an idler axle that extends from the pivot block in a substantially perpendicular direction to the direction of rotation of the pivot block with respect to the fixed block and a parallel direction to the drive shaft. The drive roller further includes a channel around its outer circumferential surface that includes a series of teeth to drive the strand of filament.